How to remove lighting and keep objects visible
You can try to change the rendering engine to “workbench” and set the shading as flat. Although if you have textures and material you may can’t use that.
If so, try switching to EEVEE/Cycles. Set the color (I’m not sure what it’s called, but maybe a color correction?) to “Standard” instead of “filmic “. It’s located on the color management, properties tab. Then, delete all shader and replace it with an image texture/color (just the emission). Without a shader, the final result should be flat without shading. You can also mess with the world setting for better result.
(If you’re confused about the emission, it’s using only image/color, like ColorRamp, image texture, noise texture, other textures, and yeah stuff like that. I believe it would work)
Oh, and I remember NVDIA GauGan is using a color mapping (if it’s what it called.) There shouldn’t be any texture on the material, isn’t it?